A Review of Building Evacuation Models - NIST Virtual Library

A.3 TIMTEX
Developer: S.S. Harrington, University of Maryland, U.S.
Purpose of the model: The TIMTEX model was developed to model evacuation from buildings
4 to 15 stories high with consideration of certain human factors, such as occupant decision on
stair use 7 .
Availability to the public for use: Since it was released as a Master’s thesis, this model is
inherently available to the public.
Modeling method: This is a movement model.
Structure of model: This is a coarse network system. Instead of acknowledging the entire floor
plan, TIMTEX concentrates on movement from the corridor on the floor to the stairs and then to
the exits. The model mainly focuses on the corridor and stair sections of the building.
Perspective of model: The model views the occupants globally as a certain number of
occupants per floor moving as a homogeneous mass to the exits. The model sees all occupants
as alert and able bodied. The occupants view the building with an individual perspective
because the user can choose the flow split of occupants to the stairs. The occupants will not
necessarily move to the closest stair. Instead, the user can either claim that a stair is frequently
used and TIMTEX will use the default percentage use of the popular stair, which is a 64 %
increase, or the user can enter any kind of flow split they want for the floor plans. In this case, it
would be possible for the user to model a certain percentage of the population using the main
exit, which may be the most familiar.
Occupant behavior: None.
Occupant movement: TIMTEX uses the equations specified in the SFPE Handbook 8 to move
occupants throughout the corridors and stair systems. The speed and flow are dependent upon
density through each component. Also, the model uses the Handbook’s rules to handle all
transition points (i.e., merging streams, where egress elements dimensions change, etc.). Flow
up stairs is 10 % slower than down stairs, as specified by Pauls 9 . If queuing occurs in the stairs,
the model assumes that the upper floors dominate the flow. There are no variations in the speed,
dependent upon the conditions or types of occupants. Instead, flow and density calculations are
based on values from the Handbook (which have been averaged among occupant types).
The user enters in either the building population per floor or the area of each floor, and the
model will enter in the number of occupants for that occupancy type (building occupancy uses
212 ft 2 /person, as an example). Again, it is up to the user to accept the flow split generated by
TIMTEX or enter a new split.
Output: Total evacuation time and individual floor clearing times are included in the output and
are shown in Figure A.4.
A-8